Apparatus for conveying glass panes through a processing plant

ABSTRACT

Apparatus for producing a jerk-free intermittent conveying motion which proceeds in accordance with a desired law of motion includes an electric motor driving the input of a steplessly variable transmission the output of which drives a crank transmission through a wormgear. A toothed push rod connected to the crank of the crank transmission drives a pinion coupled to drive one of two sprocket wheels carrying an endless chain to which is attached a carriage to be reciprocated. A cam disposed on the shaft of the crank has a control surface which defines the desired law of motion and is followed by a roller carried by one arm of a lever pivoted intermediate its ends. The other arm of the lever is coupled to an adjusting element of the steplessly variable transmission so as to adjust the output speed of such transmission in dependence upon the crank position and in accordance with the desired law of motion.

United States Patent Klotzbach 1 1 Oct. 24, 1972 {54] APPARATUS FORCONVEYING GLASS 1,833,607 11/1931 Greenfield ..74/368 PANES THROUGH APROCESSING 2,345,927 4/1944 Foster ..74/568 PLANT 2,597,357 5/1952McCormick...-. ..322/28 [72] Inventor: Kurt Klotzbach DusseldorflRath,3,215,042 11/1965 Holley, Jr. ..74/60 Germany I Primary Examiner-WilliamF. ODea [73] Assignee: SACK Glastechnik GmbH, Dussel- AssistantExaminerWesley S. Ratliff, Jr.

dorg-Rath, Germany Attorney-Singer, Stern and Carlberg [22] Filed: June4, 1970 [57] ABSTRACT [21] Appl' 43353 Apparatus for producing ajerk-free intermittent conveying motion which proceeds in accordancewith a [30] Foreign Application Priority Data desired law of motionincludes an electric motor driving the input of a steplessly variabletransmission the June 1969 Germany 19 30 0813 output of which drives acrank transmission through a 52] U S Cl 74/37 74/393 74/568 FS wormgear.A 'toothed push rod connected to the crank [51] 'C i716! 19,66 of thecrank transmission drives a pinion coupled to [58-] Fie'ld 568 drive oneof two sprocket wheels carrying an endless & chain to which is attacheda carriage to be 7 reciprocated. A cam disposed on the shaft of the [56]References Cited crank has a control surface which defines the desiredlaw of motion and is followed by a roller carried by UNITED STATESPATENTS one arm of a lever pivoted intermediate its ends. The

other arm of the lever is coupled to an adjusting ele- 3,301,244 1/1967Renshaw ..74/393 ment of the steplessly Variable transmission so as to2395803 3/1946 Bruckner et "74/393 adjust the output speed of suchtransmission in depeni? gxler g dence upon the crank position and inaccordance with reins th d 1 f 2,103,826 12/1937 Robertson ..74/79 e eweaw 0 mo 1,387,173 8/1921 Powell ..74/79 5 Claims, 5 Drawing Figures I 2224 ,1 v f New (2D I I /E"T tQ'+ r a l i -l- ,2 1m .15.

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A iiom e/s BACKGROUND The invention relates to apparatus for generatinga 5 conveying motion which proceeds in accordance with a desired law ofmotion.

The invention finds particular application in a conveying system bymeans of which sheets of glas'sare conveyed through a tempering furnace.In conveying batches of glass panes suspended on retaining tongs, forexample when passing glass panes through a tempering furnace, there isthe practical difficulty that the conveying motion causes the panes tooscillate or rock. Under these circumstances it may happen that thepanes become detached from the tongs and are broken. Moreover, it isdifficult for the bending tools of a bending station adjoining thetempering furnace to align a pane which swings to and fro.

Attempts have therefore been made to prevent the rocking of the panes byconveying apparatus which convey said panes through the temperingfurnace in accordance with a velocity characteristic which varies inaccordance with the sine function (Federal German Pat No. l 061 487).Mechanical apparatus which utilizes the motional law of Cardan joints isused to generate the sinusoidal motion. However, it has been shown thatthis transmission apparatus cannot prevent rocking of the panes. Thereason is due to the fact that a velocity characteristic correspondingto the sine function is associated with an acceleration characteristicin accordance with the cosine function. A transmission of the kindheretofore described is therefore not able to move the panes inshock-free" manner, that is to say increasing steadily from velocityzero and decreasing again, and to move them in jerk-free manner, that isto say also from zero without any step in the acceleration curve,because the sinusoidal curve and the cosine curve can never reach zerosimultaneously.

The panes are also particularly endangered on being vertically loweredinto the tempering furnace because the spikes of the retaining tongswill not yet have impressed themselves into the cold glass panes. Due tothe jerky acceleration, the self-retaining tongs are partially relievedof the weight of the panes and the clamping force of the tongs is thusreduced to such an extent that the panes may become detached from thetongs and break.

An irregular acceleration characteristic when the tempered panes arelifted from the furnace and are transported to a bending or quenchingstation is equally unfavorable because in this case the clamping forceof 55 the tongs increases and the tongs penetrate even deeper into theglass which is still soft. These impressions may then be starting pointsfor glass fracture during subsequent tempering or when stresses areapplied at a later stage. Moreover, the appearance of undesirable,so-called ears is encouraged by jerky acceleration or deceleration inthe vertical direction.

The invention therefore proposes to provide apparatus by means of whichimpact-free and jerk-free conveying motion can be generated so thatoscillations of and damage to the conveyed material can be substantiallyavoided.

SUMMARY According to the invention this problem is solved by apparatusto produce an intermittent conveying motion which proceeds in accordancewith a desired law of motion for a conveying system, wherein theimprovement comprises: a steplessly variable transmission having aninput shaft and an output shaft; a motor coupled to drive the inputshaft of the steplessly variable transmission; a sliding cranktransmission for transmitting drive to the conveying system and coupledto be driven by the output shaft of the steplessly variabletransmission; adjusting means in said steplessly variable transmissionto adjust the output speed of its output shaft; and control meanscoupled to the sliding crank transmission and to the adjusting means andoperative to effect adjustment of the output speed of the steplesslyvariable transmission in dependence on the crank position of the slidingcrank transmission and in accordance with the desired law of motion.

In this way the specified-conveying stroke s is accurately maintained inall cases.

In a preferred embodiment the control means includes cam means disposedon the shaft of the crank of the sliding crank transmission and a camsensing element coupled to an adjusting element of the steplesslyvariable transmission, the cam sensing element being disposed on one armof a lever pivoted intermediate its ends and a linkage coupling theother arm of the leverv to the adjusting element of the steplesslyvariable transmission. This construction of the control means permitssimple transmission of the controlling variable to the steplesslyvariable transmission. Moreover, cams havinga control surface or a camrise curve which corresponds to a desired law of motion can be producedrelatively simply on numerically controlled machine tools. In anadvantageous further development it is provided that the linkage whichcouples the double lever to the adjusting element is constructed to beof adjustable length and for the point at which the linkage acts on thesaid other arm of the lever to be displaceable to vary the effectivelever length of said other lever arm. By virtue of this doubleadjustability it is possible for the starting position of the adjustingelement of the steplessly variable transmission to be accurately set andit is also possible for the control deflection of the lever andtherefore of the regulating range of the steplessly variabletransmission to be varied.

To enable the conveying stroke to be adapted to different requirementsit is advisable that the point at which a push rod is pivotallyconnected to the crank of the sliding crank transmission be displaceableto enable the effective crank length to be varied.

In a preferred further embodiment of the apparatus according to theinvention, the control surface of the cam means is formed by a flexiblesteel band the two ends of which are joined, the curvature along thecircumference is adapted to be variable by means of a plurality ofadjusting elements, for example adjusting screws. By virtue of theadjustability of its control surface formed by the steel band, it ispossible for a cam constructed in this manner to substitute for aplurality of cams otherwise required for different motional laws.

BRIEF DESCRIPTION OF THE DRAWINGS Other objects and advantages of theinvention will be apparent from the following detailed description of apreferred embodiment given with reference to the attached drawings, inwhich:

FIG. 1 shows diagrammatically the construction of a transmissionapparatus of a conveying system for the intermittent conveying of glasspanes through a tempering furnace;

FIG. 2 is a partial view, on an enlarged scale, of the transmissionapparatus of the conveying system of FIG. 1;

FIG. 3 is a partial side view of the transmission apparatus of theconveying system illustrating control means for the automatic adjustmentof the desired law of motion;

FIG. 4 is a view of a disc cam or of the cam of the control means ofFIG. 3; and 1 FIG. 5' is a partial section along the line V-\/ of FIG.4.

DESCRIPTION OF PARTICULAR EMBODIMENT The conveying system illustrated inFIG. 1 is provided for the intermittent conveying of glass panes througha tempering furnace in which glass panes are heated to the temperaturerequired for bending or prestressing. The glass panes are suspended fromtongs 11 which in turn are mounted on conveying carriages 12. Theconveying carriages with the suspended panes are placed from above on toa rail 13 which extends through the tempering furnace and are displacedon the rail (in the drawing to the left) by means of a sliding carriagel4 disposed on an extension of the rail 13. With each conveying strokes, the sliding carriage 14, driven by an endless chain 15, traverses adistance corresponding approximately to the length of a conveyingcarriage 12. After the conveying stroke has been performed the slidingcarriage 14 is returned and a fresh conveying carriage 12 with suspendedpane 10 is inserted into the space between the sliding carriage and thepreviously displaced conveying carriage. During the next conveyingstroke the freshly inserted conveying carriage will be displaced and inturn displace the conveying carriages 12 disposed in front of it on therail. The conveying carriages 12 arriving at the end of the temperingfurnace are guided in suitable manner from the furnace whereupon theheated panes 10 are transferred to the next operating station, forexample a bending station.

The endless chain 15, which passes over two sprocket wheels 16 and 17,is driven by means of a pinion 19, joined to the sprocket wheel 17 by ashaft 18, a gear tooth system of a push rod 20 of a sliding crank drive20, 21 being adapted to engage with the aforementioned pinion 19. Thecrank 21 of the sliding crank transmission is disposed on the outputshaft of a wormgear transmission 22 the input shaft of which is coupledto the output shaft of a transmission 23 whose output speed issteplessly variable. The steplessly variable transmission 23 is drivenby an electric motor 24, for example a three-phase, squirrel-cage brakemotor. When the electric motor 24 is switched on it drives thesteplessly variable transmission 23. Unless said transmission is set toan output speed of zero, said transmission drives the sliding cranktransmission 21, 20 through the wormgear transmission 22, the slidingcrank transmission moving the chain 15 via the pinion 19, the shaft 18and the sprocket wheel 17 at first to the left and after a half rotationof the crank 21 once again to the right. After a complete crank rotationeach chain link of the chain 15 will be once again in the positionwhich'it occupied prior to the beginning of the crank rotation. Thevelocity with which the chain 15 and therefore the sliding carriage 14coupled thereto is moved may therefore be steplessly varied byappropriate adjustment of the output speed of the transmission 23.

Panes 10 heated to near the softening temperature must be conveyed insuch a way that the panes cannot be excited into oscillatory or rockingmovements which may result in the panes being damaged at the pointswhere they are gripped by the tongsor dropping out of the tongs 11 andwhich render more difficult the bending of the panes following theheating thereof because the panes swinging to and fro must first bestopped before they can be aligned with the bending tools.

Three curve characteristics a, b and c are illustrated in FIG. 2 belowthe sliding carriage 14 to indicate the suitable velocitycharacteristics of the sliding carriage. During the conveying strokesthe sliding carriage 14 is moved from the right hand starting positionA in accordance with one of the curves a, b or 0 into the left handlimiting position. The right hand starting position A corresponds to acrank position C while the left hand limiting position B corresponds toa crank position E of the crank 21 of the sliding crank transmission.

Rocking of the panes 10 on being conveyed through the tempering furnaceis substantially avoided because the velocity of the conveying carriages12 is first steadily increased from zero and is then subsequentlysteadily decelerated to zero. It is also a consequency of a steadychange of velocity that the associated acceleration curve has no stepresponse position. Motional charac teristics of this kind are refered toas being free of impact and jerk. The motional law which is an optimumfor a certain size of pane is determined most simply by experiment.

FIG. 3 shows a control arrangement by means of which the output speed ofthe steplessly variable transmission is varied automatically inaccordance with a desired law of motion and in relation to the positionof the crank 2l.-To this end the shaft of the crank 21 has a disc cam orcam 25 disposed on it which is connected via a double lever 26 and alinkage 27 to the adjusting element 28 of the steplessly variabletransmission. At its lower end the double lever 26 is provided with acam sensing element in the form of a roller 29 which runs on the profileof the disc cam or cam 25. The roller 29 is maintained in contact withthe cam 25 by means of a spring 30. The linkage 27, which extends to thesteplessly variable transmission 23, is adapted to slide in a slot 31 atthe other end of the double lever 26 and is lockably pivoted within saidslot. By displacement of the pivoting point in the slot 31 it ispossible for the effective lever length of one lever arm of the doublelever to be varied in a simple manner. Furthermore, the length of thelinkage 27 which extends to the adjusting element 28 of the steplesslyvariable transmission 23, may be varied by a construction similar tothat of a turn 12 is provided on the crank 21. It will beclear thatvarying the effective crank length will vary the stroke s. Such avariation of the length of the crank in the present example is achievedby constructing the crank 21 in two parts. The individual sections 32and 33 of the crank are adapted for telescoping into each other in thelongitudinal direction and, after adjustment, they may be fixed relativeto each other by means of clampingscrews or the like. In order to ensureconstant mesh of the push rod 20, having a tooth system 34, with thepinion 19, the rear side of said push rod 20 is provided with a thrustwheel 35 bearing thereon. The thrust wheel 35 is connected to the pinion19 and pivots around the central axis thereof to enable it to adjustitself to the angular position of the push rod during one crankrotation.

The velocity characteristic of the sliding carriage 14 is definedsubstantially by the shape of the cam 25. FIGS. 4 and 5 show a cam 25which permits variation of its control characteristic so that it neednot be changed if any modification of the motional characteristic of theconveying carriage is required. The adjustability of the cam is obtainedby virtue of the fact that the profile surface is formed by a flexiblesteel band 36 which is bent together to form a closed cam. Said steelband is connected to the boss 37 of the cam by means of a plurality ofradially outwardly orientated adjusting screws 38 which are distributedalong the circumference of the .boss. The ends of the steel band aresecured on a boss extension 39 of the boss 37. It is recommended thatthe boss 37 of the cam be given a shape which approximates the shape ofthe control surface of the cam so that the necessary adjustment of thecontrol surface formed by the steel band 36 is minimized. At its innerend each adjusting screw 38 is provided with a hexagonal socket'40 whichpermits radial adjustment of the screws by means of a hexagonal socketkey. Supporting pads 41, to support the steel band, are provided betweenthe adjusting screws and said steel band. Each adjusting screw 38 has apin extension 42 adapted to engage in a bore of the respectivesupporting pad 41 to retain such pad.

To perform a conveying step the motor 24 is set in motion. The slidingcarriage 14 will then be disposed in the right hand starting position Acorresponding to the crank position C. The cam 25 is shaped in such away that it adjusts the steplessly variable transmission 23, inparticular a hydraulic transmission, to a very slow output speed, thatis to say a very high transmission ratio. Since the electric motor 24does not immediately reach its full speedfor example 1,500 revlmin-whenit is switched on but requires a certain period of time for running up,the output from the steplessly variable transmission will not commencein an impulsive manner but will start slowly from zero speed.Accordingly, the worm gear transmission which follows and the crank 21of the sliding crank transmission 20, 21 disposed on the output shaft ofthe worm gear transmission is therefore set in motion slowly. At thesame time the cam 25 is rotated and, by means of the double lever 26 andthe linkage 27, regulates a progressively higher output speed of thesteplessly variable transmission 23. This means that the slidingcarriage 14 starts slowly from Zero and is accelerated in accordancewith the cam shape. Approximately when reaching the crank position D thevelocity of the sliding carriage 14 is once again reduced by anappropriate shape of the control surface of the cam 25 so that thevelocity is almost equal to zero immediately before reaching the crankposition E. On reaching point E the conveying direction of the chain 15is reversed and the sliding carriage 14 is retracted into the startingposition A. Since this return motion is not accompanied by anydisplacement of the conveying carriage 12, it can be made to proceedsubstantially faster than the conveying stroke s if the control surfaceof the cam is appropriately constructed. A limit switch 21 operated bythe crank 21 will then ensure that the electric motor 24 is switched offin sufficient time to enable the crank to come to a stop at the positionC. The next conveying stroke s will be performed after the nextconveying carriage 12 with the suspended pane is placed upon the rail13. The conveying stroke may be triggered automatically if the electricmotor 24 is switched on by. the conveying carriage which has just beennewly placed on the rail.

The transmission described hereinabove is of course not confined to thehorizontal conveying of panes through a tempering furnace but may alsobe employed for the vertical lowering into the tempering furnace'or forthe lifting of the tempered panes from the tempering furnace. To thisend it is merely necessary for the push rod of the sliding cranktransmission to be connected to the conveyor for the vertical motion ofthe pane. In general, apparatus embodying the invention may be employedwherever it is advantegous if the material to be transported isaccelerated or decelerated in accordance with a defined law of motion.

Iclaim: I

l. In an apparatus for conveying glass panes in a shock-free mannerthrough a treatment furnace while supporting said glass panes on carriermeans intermittently movable along said furnace under the action ofreciprocably mounted operating means engageable with said carrier means,a drive motor, a crank arm mounted for rotation about a fixed axis, aconnecting rod pivotally connected with said crank arm, meansoperatively connecting said connecting rod with said reciprocableoperating means, mechanism drivingly connecting said motor with saidcrank arm, said mechanism including an infinitely variable transmissionmeans, cam means secured to said crank arm for rotation therewith aboutsaid fixed axis, follower means associated with said cam means, linkagemeans connecting said follower means with said transmission means forvarying the transmission rate thereof, and a limit switch operable bysaid crank arm for limiting the operation of said crank arm to onecomplete revolution.

2. The apparatus according to claim 1, including means for varying thelength of said linkage means.

3. The apparatus according to claim 1, including means for varying thelength of said crank arm.

4. In an apparatus for conveying glass panes in a shock-free mannerthrough a treatment furnace while supporting said glass panes on carriermeans intermittently movable along said furnace under the action ofreciprocably mounted operating means engageable with said carrier means,a drive motor, a crank arm mounted for rotation about a fixed axis, aconnecting rod pivotally connected with said crank arm, meansoperatively connecting said connecting rod with said reciprocableoperating means, mechanism drivingly connecting said motor with saidcrank arm, said mechanism including an infinitely variable transmissionmeans, cam means secured to said crank arm for rotation therewith aboutsaid fixed axis, said cam means including a peripheral flexible steelband and means for varying the curvature of said steel band to therebyvary the contour of said cam means, follower means associated with saidcam means, linkage means connecting said follower means with saidtransmission means for varying the transmission rate thereof, and alimit switch operable by said crank arm for limiting the operation ofsaid crank arm to one complete revolution.

5. In an apparatus for conveying glass panes in a shock-free mannerthrough a treatment furnace while supporting said glass panes on carriermeans intermittently movable along said furnace under the action ofreciprocably mounted operating means engageable with said carrier means,a continuously rotatable drive motor, a crank arm mounted for rotationabout a fixed axis, a connecting rod pivotally connected with said crankarm, means operatively connecting said connecting rod with saidreciprocable operating means and adapted to impart reciprocatorymovement to said reciprocable operating means as said crank arm isrotated, mechanism drivingly connecting said motor with said crank arm,said mechanism including a transmission means infinitely variablebetween a minimum and a maximum transmission rate, cam means secured tosaid crank arm for rotation therewith about said fixed axis, followermeans associated with said cam means, linkage means connecting saidfollower means with said transmission means, said cam means including aperipheral flexible steel band and means for varying the curvature ofsaid steel band to thereby vary the contour of said cam means, wherebysaid transmission rate is varied in dependence upon the contour of saidcam means to impart correspondingly varying reciprocal velocity to saidreciprocably mounted operating means, and a limit switch operable bysaid crank arm for limiting the operation of said crank arm to onecomplete revolution.

1. In an apparatus for conveying glass panes in a shock-free mannerthrough a treatment furnace while supporting said glass panes on carriermeans intermittently movable along said furnace under the action ofreciprocably mounted operating means engageable with said carrier means,a drive motor, a crank arm mounted for rotation about a fixed axis, aconnecting rod pivotally connected with said crank arm, meansoperatively connecting said connecting rod with said reciprocableoperating means, mechanism drivingly connecting said motor with saidcrank arm, said mechanism including an infinitely variable transmissionmeans, cam means secured to said crank arm for rotation therewith aboutsaid fixed axis, follower means associated with said cam means, linkagemeans connecting said follower means with said transmission means forvarying the transmission rate thereof, and a limit switch operable bysaid crank arm for limiting the operation of said crank arm to onecomplete revolution.
 2. The apparatus according to claim 1, includingmeans for varying the length of said linkage means.
 3. The apparatusaccording to claim 1, including means for varying the length of saidcrank arm.
 4. In an apparatus for conveying glass panes in a shock-freemanner through a treatment furnace while supporting said glass panes oncarrier means intermittently movable along said furnace under the actionof reciprocably mounted operating means engageable with said carriermeans, a drive motor, a crank arm mounted for rotation about a fixedaxis, a connecting rod pivotally connected with said crank arm, meansoperatively connecting said connecting rod with said reciprocableoperating means, mechanism drivingly connecting said motor with saidcrank arm, said mechanism including an infinitely variable transmissionmeans, cam means secured to said crank arm for rotation therewith aboutsaid fixed axis, said cam means including a peripheral flexible steelband and means for varying the curvature of said steel band to therebyvary the contour of said cam means, follower means associated with saidcam means, linkage means connecting said follower means with saidtransmission means for varying the transmission rate thereof, and alimit switch operable by said crank arm for limiting the operation ofsaid crank arm to one complete revolution.
 5. In an apparatus forconveying glass panes in a shock-free manner through a treatment furnacewhile supporting said glass panes on carrier means intermittentlymovable along said furnace under the action of reciprocably mountedoperating means engageable with said carrier means, a continuouslyrotatable drive motor, a crank arm mounted for rotation about a fixedaxis, a connecting rod pivotally connected with said crank arm, meansoperatively connecting said connecting rod with said reciprocableoperating means and adapted to impart reciprocatory movement to saidreciprocable operating means as said crank arm is rotated, mechanismdrivingly connecting said motor with said crank arm, said mechanismincluding a transmission means infinitely variable between a minimum anda maximum transmission rate, cam means secured to said crank arm forrotation therewith about said fixed axis, follower means associated withsaid cam means, linkage means connecting said follower means with saidtransmission means, said cam means including a peripheral flexible steelband and means for varying the curvature of said steel band to therebyvary the contour of said cam means, whereby said transmission rate isvaried in dependence upon the contour of said cam means to impartcorrespondingly varying reciprocal velocity to said reciprocably mountedoperating means, and a limit switch operable by sAid crank arm forlimiting the operation of said crank arm to one complete revolution.